Bac-to-Bac系统双表达mChIL18基因和H5亚型AIV HA1基因及其免疫原性

为了制备禽流感病毒(avian influenza virus,AIV)基因工程亚单位疫苗,将其HA1基因和鸡IL-18成熟蛋白基因(mChIL-18)分别或先后插入到双表达载体pFastBacTM Dual中,表达单表达或双表达蛋白pHA1、pIL18和pHA1-IL18。将表达蛋白和/或禽流感二价(H5+H7)灭活疫苗通过腿部肌肉多点注射免疫7日龄SPF鸡,2周后加强免疫1次。结果显示,pHA1-IL18、pHA1+pIL18、pIL18+禽流感疫苗、禽流感疫苗和pHA1免疫雏鸡后均能促进CD4+T、CD8+T细胞的增殖和抗体水平的增加,且pHA1-IL18免疫组要优于pHA1+pIL18混合免疫组及其他免疫组和对照组,差异显著(P0.05)。结果表明,pHA1-IL18可以产生比pIL18+pHA1更强的免疫原性,为新型疫苗的研制奠定基础。     

Effects of dietary protein/phosphate restriction in normal dogs and dogs with chronic renal failure

The effects of three dietary protein intakes (1–9, 1–3, and 0–6 g protein/kg bodyweight/day) on selected aspects of protein, mineral and electrolyte balance as well as renal functions was studied in normal dogs with moderate chronic renal failure. Dietary phosphate levels varied according to the quantity of phosphate in protein sources. Within the ranges of protein intake examined in this study, protein intake did not have a significant effect on glomerular filtration rates as measured by inulin clearance or 24-hour creatinine clearance. Restricting protein intake to less than 1–9 g protein/kg bodyweight/day further reduced retention of nitrogenous waste products as measured by serum urea nitrogen concentrations, but at the expense of adequate protein nutrition. Diets providing less than 1–9 g protein/kg bodyweight/day promoted protein malnutrition characterised by hypoproteinaemia and hypoalbuminaemia in both normal dogs and dogs with renal failure. Serum protein concentrations were similar in normal and renal failure dogs, suggesting that, under the conditions of this study, normal and renal failure dogs may have similar protein requirements. Progressive dietary protein/phosphate restriction improved but did not normalise phosphate balance in renal failure dogs.     

Pharmacokinetic behavior in sheep and cattle of 5-chloro-2-(methylthio)-6-(1-naphthyloxy)-1H-benzimidazole, a new fasciolicide agent

The physicochemical properties, p K _a, Log P and solubility of compound alpha, (5-chloro-2-(methylthio)-6-(1-naphthyloxy)-1 H -benzimidazole), a new fasciolicide agent, were characterized using conventional methods. Also, its pharmacokinetics was evaluated in sheep and cattle. In both species an oral dose of 12 mg/kg was administered. Blood samples were collected during 144 h and analyzed by using an HPLC assay. Results showed that compound alpha is a weak base with a p K _a value of 2.87 and log P of 1.44. The solubility was very low in aqueous solvents. Pharmacokinetic studies showed that in both species compound alpha could not be detected at any sampling time. The mean half-life ( t _½) values of alpha sulphoxide in sheep and cattle were 19.86 and 29.87 h, while the half-life values of alpha sulphone were 19.43 and 46.32 h respectively. C _max values of alpha sulphoxide did not differ between species while alpha sulphone values were higher in cattle. Plasma protein binding of alpha sulphoxide was between 82% and 86%. These results, combined with the previous efficacy studies, suggest that compound alpha could be a promising fasciolicide agent.     

Hydrolysis of phytic acid by intrinsic plant and supplemented microbial phytase (Aspergillus niger) in the stomach and small intestine of minipigs fitted with re-entrant cannulas. 3. Hydrolysis of phytic acid (IP6) and occurrence of hydrolysis products (IP5, IP4, IP3 and IP2)

Hydrolysis of phytate in the stomach and the small intestine as influenced by intrinsic plant (wheat) and supplemented microbial phytase (Aspergillus niger) were investigated with six minipigs (40-50 kg initial body weight) fitted with re-entrant cannulas in the duodenum, 30 cm posterior to the pylorus (animals 1, 4, 5 and 6) and ileocecal re-entrant cannulas, 5 cm prior the ileocecal junction (animals 1, 2 and 3), respectively. Dietary treatments were as follows: (1) diet 1, a corn-based diet [43 U phytase/kg dry matter (DM)]; (2) diet 2, diet 1 supplemented with microbial phytase (818 U/kg DM); and (3) diet 3, a wheat-based diet (1192 U/kg DM). At 07 30 h and 19 30 h, each animal was fed 350 g diet mixed with 1050 ml de-ionized water. Digesta were collected continuously and completely during a 12-h period after feeding. Mean hydrolysis rates of IP6 in the stomach as measured at the proximal duodenum of animals 1, 4, 5 and 6 were 9.0, 77.2 and 66.2% for diet 1, 2 and 3, respectively. Microbial phytase was much more effective in phytate hydrolysis than wheat phytase. Mean IP6 hydrolysis rates of the respective diets in the stomach and small intestine as measured at the distal ileum of animals 1, 2 and 3 were 19.0, 62.6 and 64.6% and were lower than treatment means of the stomach only. Differences existed between experimental animals with respect to their ability to hydrolyse IP6 in the stomach independent of the presence and source of dietary phytase. Considerable amounts of hydrolysis products occurred in both the duodenal and ileal digesta when diets 2 and 3 were fed; however, only traces were determined after ingestion of diet 1. Independent of dietary treatment, four IP5 isomers were detected, but in different amounts.     

日粮能量和蛋白质水平对5～10周龄仔鹅生产性能的影响

选用4周龄扬州鹅180只,以能量和蛋白质为试验因子,采用2因素3水平设计,研究日粮能量和蛋白质水平对生长期扬州鹅生产性能的影响。研究结果表明:①10周龄体重和日增重各组间差异不显著(P>0.05),屠宰指标间无明显规律。②对体重、日增重、屠宰率和腿肌率的影响,均是互作>能量>蛋白质,其中互作和能量对腿肌率的影响极显著(P<0.01);对半净膛率和全净膛率的影响,均是能量>互作>蛋白质,且影响均不显著(P>0.05);对胸肌率的影响,是能量>蛋白质>互作,且影响不显著(P>0.05)。③第7组(低能高蛋白组)在生长性能和经济效益方面均较佳。因此,推荐5￣10周龄仔鹅日粮能量、蛋白质水平分别为10.50MJ/kg、17%。     

Effects of dietary protein and growth hormone-releasing peptide (GHRP-2) on plasma IGF-1 and IGFBPs in Holstein steers

This study was conduct to determine the influence of dietary protein on the response of plasma insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding proteins (IGFBPs) to exogenous growth hormone releasing peptide-2 (GHRP-2 or KP 102) in Holstein steers. Eight 16-month-old Holstein steers were grouped by liveweight to two feeding treatments; high protein (HP; CP 1.38 kg/day and TDN 4.5 kg/day DM intake, n=4) or low protein (LP; CP 0.66 kg/day and TDN 4.42 kg/day DM intake, n=4). The experiment was a single reverse design whereby each group was injected twice daily with GHRP-2 (12.5 microg/kg body weight (BW)/day) or saline solution into the jugular vein for a 6-day period. Plasma IGF-1 in the HP group were higher than in the LP group (P<0.05), but plasma 34 kDa IGFBP-2 was lower in the HP than the LP group (P<0.05). The amplitude of the maximum growth hormone (GH) peaks responding to GHRP-2 injection were higher at day 1 than at day 6 of saline or GHRP-2 treatment in both LP and HP steers (P<0.05). The area under the GH response curve for 180 min after the GHRP-2 injection was not significantly different between the LP and the HP groups at days 1 and 6. A response in plasma IGF-1 concentration to GHRP-2 treatment in the HP group was observed at day 1 (198.9+/-18.1 ng/ml), day 2 (195.2+/-21.1 ng/ml) and day 6 (201.3+/-14.8 ng/ml) (P<0.05). No increase in plasma IGF-1 was observed from GHRP-2 administration in the LP group. Although the response of plasma IGF-1 concentration to GHRP-2 administration was increased in the HP group (P<0.05), there was no apparent effect of GHRP-2 treatment on plasma 38-43 kDa IGFBP-3 and 34 kDa IGFBP-2 at days 2 and 6 of treatment. In conclusion, it is proposed that the 34 kDa IGFBP-2 is sensitive to dietary protein level and may play an important role in the regulation of circulating IGF-1 in ruminant. In addition, increased plasma IGF-1 concentration observed in the HP group in response to the GHRP-2 treatment did not appear to affect plasma IGFBPs.     

Lactational and subsequent reproductive responses of lactating sows to dietary lysine (protein) concentration

Gilts (n = 208) were used to evaluate the effect of lysine (protein) intake over three parities on lactation and subsequent reproductive performance. Sows were assigned randomly to one of five experimental diets at each farrowing. The five corn-soybean mealbased lactation diets contained increasing concentrations of total lysine (.60, .85, 1.10, 1.35, and 1.60%) and CP (14.67, 18.15, 21.60, 25.26, and 28.82%). Other amino acids were provided at a minimum of 105% of the NRC (1988) ratio to the lysine requirement. Sows had ad libitum access to their assigned diets from parturition until weaning (19.5+/-.2 d postpartum). All sows were fed a common gestation diet (14% CP and .68% lysine) from weaning to next farrowing. Litter size was standardized by d 3 postpartum to 10 pigs in parity 1 and 11 pigs in parity 2 and 3. Increasing dietary lysine (protein) linearly decreased (P<.05) voluntary feed intake of parity 1 (from 5.4 to 4.6 kg/d), 2 (from 6.5 to 5.8 kg/d), and 3 sows (from 6.8 to 6.2 kg/d). With the increase of dietary lysine (protein) concentration during lactation, litter weight gain responded quadratically (P<.05) in all three parities. Maximal litter ADG was 2.06, 2.36, and 2.49 kg/d in parities 1, 2, and 3, respectively, which occurred at about 44, 55, and 56 g/d of lysine intake for parity 1, 2, and 3 sows, respectively. Increasing dietary lysine (protein) had no effect (P>.1) on sow weight change, weaning-to-estrus interval, and farrowing rate in all three parities and no effect on backfat change in parity 2 and 3, but tended to increase backfat loss linearly (P<.1) in parity 1. A linear decrease of second litter size (total born, from 11.7 to 10.1, P<.1; born alive, from 11.0 to 8.9, P<.01) was observed when dietary lysine (protein) increased during the first lactation. Lysine (protein) intake during the second lactation had a quadratic effect on third litter size (P<.05; total born: 13.3, 11.2, 11.6, 11.9, and 13.6; born alive: 11.8, 10.1, 10.3, 11.2, and 12.4). However, fourth litter size was not influenced by lysine (protein) intake during the third lactation. These results suggest that the lysine (protein) requirement for subsequent reproduction is not higher than that for milk production. Parity influences the lysine (protein) requirement for lactating sows and the response of subsequent litter size to previous lactation lysine (protein) intake.     

Differential expression of bone morphogenetic protein 4-6 (BMP-4, -5, and -6) and growth differentiation factor-9 (GDF-9) during ovarian development in neonatal pigs

Growth differentiation factor-9 (GDF-9) and bone morphogenetic proteins (BMPs), comprise the largest subgroups of ligands in the TGF-β superfamily, and have been shown to be involved in follicle development in mammals. However, whether these factors are involved in folliculogenesis in pigs is still unknown. The present study was performed to determine the relationships between early folliculogenesis and the expression of GDF-9 and BMP (BMP-4, -5 and -6) mRNAs in neonatal pigs. Ovaries were removed at 5, 16, 28 and 39 days after birth to examine the follicular population (the right ovary of each animal) and to detect mRNA expression (the left ovary of each animal). Primordial follicles accounted for >80% of the ovarian follicles from 5 days until 39 days after birth. A marked increase in primary follicles and the appearance of secondary follicles were observed in the ovaries at 28 days after birth. BMP-4, -5, and -6 and GDF-9 mRNAs were expressed by ovaries at 5-, 16-, 28- and 39-day-old pigs. The peak expression of BMP-4, -5, and -6 and GDF-9 mRNAs was observed in the ovaries at 5, 39, 28 and 16 days, respectively, after birth. These data demonstrate that folliculogenesis in piglets might be controlled by the interaction with these factors. We conclude that BMPs and GDF-9 may have distinct functions in several stages of follicle development in neonatal pig ovaries.     

莪术油复方口服液对禽流感病毒H5N1亚型的抑制作用和攻毒保护试验

利用从中药莪术中提炼的莪术油制成的莪术油复方口服液,与鸡源禽流感病毒(AIV)H5N1在10日龄非免疫鸡胚中相互作用,观察莪术油复方口服液对禽流感病毒H5N1的抑制效果;用莪术油复方口服液对14日龄非免疫试验鸡连续口服喂药1周,采用禽流感病毒H5N1攻击鸡群,观察药物对鸡的保护效果。结果表明,在体外抑制试验中,0.25%、0.5%和1%的莪术油复方口服液对鸡胚为无毒浓度,对鸡胚的保护作用分别为60%、80%和80%;0.75%、1.5%和3%的莪术油复方口服液对试验鸡的保护作用分别为80%、100%和100%。病理组织检查结果表明鸡的肺脏无病变,并且增强了脾脏的免疫功能。初步结果显示,莪术油复方口服液对禽流感病毒具有显著的抑制作用。     

Comparison of high (5%) and low (1%) concentrations of micellar microemulsion propofol formulations with a standard (1%) lipid emulsion in horses

OBJECTIVE: To compare anesthesia-related events associated with IV administration of 2 novel micellar microemulsion preparations (1% and 5%) and a commercially available formulation (1%) of propofol in horses. Animals-9 healthy horses. PROCEDURES: On 3 occasions, each horse was anesthetized with 1 of the 3 propofol formulations (1% or 5% microemulsion or 1% commercial preparation). All horses received xylazine (1 mg/kg, IV), and anesthesia was induced with propofol (2 mg/kg, IV). Induction and recovery events were quantitatively and qualitatively assessed. Venous blood samples were obtained before and at intervals following anesthesia for quantification of clinicopathologic variables. RESULTS: Compared with the commercial formulation, the quality of anesthesia induction in horses was slightly better with the micellar microemulsion formulas. In contrast, recovery characteristics were qualitatively and quantitatively indistinguishable among treatment groups (eg, time to stand after anesthesia was 34.3 +/- 7.3 minutes, 34.1 +/- 8.8 minutes, and 39.0 +/- 7.6 minutes in horses treated with the commercial formulation, 1% microemulsion, and 5% microemulsion, respectively). During recovery from anesthesia, all horses stood on the first attempt and walked within 5 minutes of standing. No clinically relevant changes in hematologic and serum biochemical analytes were detected during a 3-day period following anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the micellar microemulsion preparation of propofol (1% or 5%) has similar anesthetic effects in horses, compared with the commercially available lipid propofol formulation. Additionally, the micellar microemulsion preparation is anticipated to have comparatively low production costs and can be manufactured in various concentrations.     

Effects of breed (Angus vs Simmental) and copper and zinc source on mineral status of steers fed high dietary iron

Forty-four Angus (n = 24) and Simmental (n = 20) steers, averaging 301 kg initially, were used to determine the effects of breed and Cu and Zn source (SO4 or proteinate (Prot) form) on Cu and Zn status of steers fed high dietary iron (Fe). Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of: 1) CuSO4 + ZnSO4 ,2) CuSO4 + ZnProt, 3) CuProt + ZnSO4, and 4) CuProt + ZnProt. Copper and Zn sources were added to provide 5 mg Cu and 25 mg supplemental Zn/kg DM. All steers were individually fed a corn silage-based diet supplemented with 1,000 mg Fe (from FeSO4)/kg DM. Liver biopsy samples were obtained at the beginning and end of the 149-d study. Serum samples were collected initially and at 28-d intervals for determination of ceruloplasmin activity and Zn and Cu concentrations. Copper and Zn source did not affect performance, serum or liver Cu and Zn concentrations, or ceruloplasmin activity. Copper status decreased (P < 0.01) in all steers with time, and increasing the level of supplemental Cu from 5 to 10 mg/kg DM on d 84 did not prevent further drops in serum Cu and ceruloplasmin. Simmental steers had lower (P < 0.05) serum and liver Cu concentrations, and serum ceruloplasmin activity throughout the study. These results indicate that neither CuSO4 nor CuProt were effective at the supplemental concentrations evaluated in alleviating the adverse effect of high Fe on Cu status. Simmental steers had lower Cu status than Angus, suggesting a higher Cu requirement.     

Molecular cloning and tissue distribution of uncoupling protein 1 (UCP1) in plateau pika (Ochotona dauurica)

Uncoupling protein 1 (UCP1) is present exclusively in brown adipose tissue, and contributes to body temperature control during cold exposure. We cloned UCP1 cDNA of plateau pika (Ochotona dauurica), a small, non-hibernating, diurnal lagomorph that inhabits in relatively cold climates and at high altitudes in Mongolia and in northern China. The nucleotide sequence of pika UCP1 was highly homologous to UCP1 of other species, and the deduced amino acid sequence had some common domains for UCP, including six mitochondrial carrier protein motifs and a putative purine-nucleotide binding site. RT-PCR and Western blot analyses revealed that both UCP1 mRNA and protein were expressed exclusively in the interscapular adipose tissue. These results suggest that pika UCP1 contributes to heat production in brown adipose tissue, as do those in other species.     

Expression of interleukin (IL)-5 and IL-9 receptors on neutrophils of horses with heaves

Heaves, a condition associated with airway neutrophilia, is believed to result from an allergic response to environmental dust particles. However, the contribution of neutrophils to the allergic response is poorly understood. It has been hypothesized that Th2-type cytokines can directly activate neutrophils to produce pro-inflammatory mediators. The present study focused on the presence of receptors for the Th2-type cytokines interleukin (IL)-5 and IL-9 on peripheral blood neutrophils of horses with heaves. Neutrophils were isolated from peripheral blood of horses with heaves (n=7), and normal control (n=5) before (pasture) and 3 weeks following a continuous natural allergen challenge (stabling). Horses with heaves had significantly increased numbers of neutrophils expressing IL-5 and IL-9 receptors compared to control while in pasture, and further increased during stabling in heaves affected horses but not in control animals. These results provide a possible mechanism by which Th2-type cytokines may activate neutrophils in equine heaves.     

Pathogenesis of Bovine herpesvirus-1 (BHV-1) infections: Interactions of the virus with peripheral bovine blood cellular components

Bovine herpesvirus-1 (BHV-1) is believed to reach the placenta via the hematogenous route as the virus has been recovered from the blood buffy coat cells of experimentally infected cattle. However, the manner in which the virus relates to these and other blood cells while in transit in the blood is not known. The nature of this relationship was investigated in the present study.

An in vitro correlate of the in vivo cell-virus interactions was simulated by isolating peripheral blood cells on a Ficoll-Hypaque gradient and testing their capacity to adsorb and act as host cells for BHV-1 replication. It was shown that all leukocytes, but not red cells, can adsorb virus readily. Of the leukocytic fraction, monocytes and lymphocytes adsorb the virus most effectively. Monocytes supported viral replication while lymphocytes could do so only after stimulation with phytohemagglutinin.

It is concluded that in vivo replicating BHV-1 is transported in monocytes, and is adsorbed to all leukocytes from which it finally reaches the placenta, leading to abortion.     

Pathophysiology of ovine fascioliasis: The influence of dietary protein and iron on the erythrokinetics of sheep experimentally infected with Fasciola hepatica

Worm-free sheep were fed diets with a high or low protein and iron content and infected with 1,000 F. hepatica metacercariae. The adult fluke burdens of the sheep on each diet were similar, but animals on the poorer plane of nutrition developed an earlier and ultimately more severe anaemia and as a result had to be necropsied earlier. By measuring the attendant changes in blood volume and erythrokinetics, it was found that the underlying cause of the anaemia in all animals was a combination of haemodilution, intra-hepatic and biliary haemorrhage, and its earlier appearance and faster development in the poorer-fed group was a refelection of the earlier onset of these changes in association with a faster rate of fluke migration. The ultimate degree of anaemia was not related to the severity of biliary haemorrhage, but rather to the animals' erythropoietic capacity. This was substantially lower in the sheep maintained on the poorer diet, which unlike their better-fed counterparts, became iron deficient by virtue of their inability to replace from the diet iron lost in the faeces as a result of haemorrhage. It was concluded that this difference was primarily a reflection of the better appetite and hence iron intake of the supplemented sheep, but differences in the efficiency of dietary iron utilization, possibly related to protein intake, may also have been involved.In a further experiment involving sheep infected with 600 metacercariae, there was no evidence of haemodilution. When provided with a diet of high protein and iron content, these animals were able to maintain constant, albeit reduced PCV values in the face of substantial biliary haemorrhage. However, when switched to an inferior diet, the same degree of haemorrhage produced a sharp fall in PCV, suggesting that erythropoiesis was adversely affected by reduced protein and iron intake.     

Lack of Modifying Effects of Intratracheal Instillation of Quartz or Dextran Sulfate Sodium (DSS) in Drinking Water on Lung Tumor Development Initiated with 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in Female A/J Mice

The purpose of the present study was to investigate the effects of inflammation, induced by intratracheal instillation (i.t.) of quartz as an environmental factor in the lung or drinking of dextran sulfate sodium (DSS) as an environmental factor in the colon on lung tumors in female A/J mice initiated with NNK. For comparison, colonic preneoplastic lesions, aberrant crypt foci (ACF), were also assessed. A/J mice at 6 weeks of age were divided into 5 groups, and Groups 1, 2 and 3 were pretreated with NNK (2 mg / 0.1 ml saline / mouse, intraperitoneal injection) at week 0. For a week, 2% DSS in drinking water was administered to the mice in Groups 2 and 4 beginning in week 1. In week 2, the mice of Groups 3 and 5 were exposed to intratracheal instillation of quartz (0.1 mg/rat) suspended in 25 μl saline. The experiment was terminated after 16 weeks. The results for the lung tumors and colonic ACFs showed a lack of modifying effects of the inflammation in either site. Hematologically and histopathologically, the inflammation induced by 0.1 mg quartz in the lung and 2% DSS in the colon was lacking or only mild at the end of 16 weeks. These results suggest that there may be differences in sensitivity to inflammation that determine tumor promoting potential.     

Glucose metabolism and regulation in lactating mink (Mustela vison)--effects of low dietary protein supply.

Eighteen lactating mink raising litters of 6 to 7 kits were fed ad libitum from parturition on diets with 32% of ME derived from protein and decreasing fat:carbohydrate ratios [high fat:low carbohydrate (HFLC): 67:1, medium fat:medium carbohydrate (MFMC): 52:16, low fat:high carbohydrate (LFHC): 37:31]. Four weeks post partum the dams were fitted with a jugular vein catheter, and the experiment started with a 3 hours fasting period, after which the dams were fed 210 kJ ME of the experimental diets. Blood samples were collected 10 and 5 min before feeding and 30, 60, 90, 120, 150 and 180 min postprandially. Two hours postprandially a single dose of 50 microCi U-14C-labelled glucose was administered to each dam and blood samples were collected 5, 10, 20, 30, 45 and 60 min after the tracer administration. Plasma concentrations of glucose and insulin 30 to 120 min postprandially were higher in dams fed the LFHC diet, than in dams fed the HFLC diet, values for dams fed the MFMC diet being intermediate. Plasma glucagon concentrations were not significantly affected by dietary treatment. The glucagon:insulin ratios decreased postprandially in all dams, the response being significant in dams fed the LFHC diet. Plasma concentrations of urea were not significantly affected by dietary treatment. Plasma FFA concentrations tended to increase postprandially in dams fed the HFLC diet. Glucose turnover rates were approximately 4.0% per min in all dams, irrespective of dietary treatment. However, the daily glucose flux was lower in dams fed the HFLC diet than in dams fed the LFHC diet, and tended to be lower than in dams fed the MFMC diet. In conclusion, a dietary protein supply of 32% of ME simultaneously with a carbohydrate supply of 16% or 31% of ME had no adverse effects on glucose homeostasis or glucose metabolism in lactating mink.     

Interrelationships between exogenous porcine somatotropin (PST) administration and dietary protein and energy intake on protein deposition capacity and energy metabolism of pigs

Exogenous porcine somatotropin (PST) administration stimulates protein deposition and inhibits lipogenesis, resulting in dose-related improvements in growth performance and reduction of carcass fat content. However, the associated impacts of this technology on dietary nutrient requirements and energy partitioning between maintenance, protein, and fat remain unclear. Studies with pigs between 25 and 60 kg body weight indicate that, because of unknown improvements in amino acid utilization and(or) in the energy available for protein synthesis, only marginal increases in dietary protein percentage are required to support 20 to 25% improvements in protein deposition induced by PST administration. In contrast, an increased dietary protein concentration is required to support maximal protein deposition in pigs 60 to 100 kg. Exogenous PST administration increased the maintenance energy requirement and altered the relationship between energy intake and protein deposition, although the magnitude of these changes and the consequent effects on expression of dietary protein (amino acid) requirements was influenced by gender. Albeit limited, information suggests that PST alters nutrient demand at the tissue level. Information of this type will form the basis for rational decisions concerning the method for expression of dietary nutrient requirements (% vs g/d) for PST-treated pigs. Further quantitative information is required on the effects of PST dosage on the relationship of protein deposition to energy intake and on any underlying changes in amino acid utilization and metabolism.